Whereas in June of last year the U.S. accounted for 62 percent of all active Twitter users, that number has fallen to 50 percent. Significant growth in countries like Germany, Brazil and Indonesia has contributed to Twitter's burgeoning international user share over the past six months.

Brazil's growth from 2 percent to 8.8 percent puts it in second place behind the United States for active Twitter users. The UK is close behind at 7.2 percent. Drilling down into users by city, London, Los Angeles, Sao Paulo, New York City and Chicago make up the top five in terms of unique users, but New York contributes the most total tweets at 2.37 percent. The data above was compiled from a study of more than 13 million unique Twitter accounts active between October 16 and December 16, 2009.

Another interesting reveal from the study is how startlingly few Twitter users have enabled the location feature that allows geographic information to be attached to their tweets. Only a paltry 0.23 percent of 10 million tweets Sysomos looked at this week were tagged with their locations.

The geolocation feature has only been live to all since November, though, so it may just take some time for the concept to reach people — and for third parties to build features that really take advantage of the location information. For now, it seems that not many people feel there's a compelling reason to enable the location service just yet.

Surely Twitter's push to launch its various language versions, including German, Italian, French, Spanish and Japanese, has contributed to its international growth spurt. Do you think international growth is the key to solving Twitter's growth problem?

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